For smooth operation, internal combustion engines require a continual metered flow of fuel from the fuel storage tank to the cylinders under varying engine demands from idle to wide open throttle. Various fuel system designs have evolved to provide such flow. Many systems employ a fuel pump and fuel pressure regulator to maintain sufficient fuel pressure in the fuel line for delivery to fuel metering devices. The fuel metering devices then selectively meter out fuel to the cylinders for combustion therein.
Many fuel systems utilize fuel injectors to meter fuel to the cylinders. The quantity of fuel metered into the cylinders can be accurately controlled by a Powertrain Control Module (PCM) by varying the injector pulse-width assuming a known constant fuel pressure between the fuel feed side of the fuel injector and the discharge side thereof. During high fuel demands, a constant pressure may not be sustained in the fuel rail, which conducts fuel to the fuel injectors, thus reducing flow of fuel to the cylinders. Should the flow of fuel to the cylinders be interrupted or reduced, the engine may run rough or stall.
In order to prevent such an event, or to assist in diagnosing engine trouble, the fuel system can be tested under dynamic and static conditions, and several such tests exist for that purpose. However, some tests require disassembly of the fuel line, while others require separate fuel reservoirs, injector drivers, or fuel system simulation equipment. These requirements necessitate specialized tools and take an inordinate amount of time to perform. In addition, some tests have used suspect, and even erroneous, methods for identifying fuel system flow reduction and restrictions. Such methods may result in false problem detection, possibly leading to unnecessary, expensive repairs.
It is an object of the present invention to provide a method for testing adequate fuel system delivery which can be quickly and accurately accomplished without false problem detection.
Another object is to provide a method for testing fuel system delivery which can be safely accomplished with a minimum number of hardware requirements.
It is an advantage of the present invention that a test according to the present invention may be accomplished without starting the engine and without breaking the fuel line, thus allowing a service technician to more quickly and conveniently inspect the fuel line.
Another advantage of the present invention is that a minimum of accessories, including a pressure transducer, a communication cable, a stand alone computer, and a power source, are required to perform the test.
A feature of the present invention is the use of vehicle specific fuel system pressure calibration data for comparison with measured fuel system pressures.